Camshaft adjusters are used in internal combustion engines for varying the control times of the combustion chamber valves, in order to be able to variably shape the phase relation between a crankshaft and a camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. The adaptation of the control times to the current load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated in a drive train by which a torque is transferred from the crankshaft to the camshaft. This drive train can be constructed, for example, as a belt drive, chain drive, or gearwheel drive.
In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of pressure chambers that act against each other and can be pressurized with hydraulic medium. The drive element and the driven element are arranged coaxially. By filling and emptying individual pressure chambers, a relative movement is generated between the drive element and the driven element. A spring with a rotating effect between the drive element and the driven element forces the drive element in a preferred direction relative to the driven element. This preferred direction can be in the same direction or in the opposite direction to the direction of rotation.
One type of hydraulic camshaft adjuster is the vane cell adjuster. The vane cell adjuster has a stator, a rotor, and a drive wheel with external teeth. As the driven element, the rotor can usually be locked in rotation with the camshaft. The drive element contains the stator and the drive wheel. The stator and the drive wheel are locked in rotation with each other or are alternatively constructed as a single piece. The rotor is arranged coaxial to the stator and within the stator. The rotor and the stator form oil chambers that act in opposite directions with their vanes extending in the radial direction and these chambers can be pressurized by oil pressure and allow a relative rotation between the stator and the rotor. The vanes are constructed either integrally with the rotor or the stator or are arranged as “inserted vanes” in grooves of the rotor or stator provided for this purpose. The vane cell adjusters further have various sealing covers. The stator and the sealing covers are secured with each other by several screw connections.
Another type of hydraulic camshaft adjuster is the axial piston adjuster. Here, a displacement element that generates a relative rotation between a drive element and a driven element by helical gearing is shifted in the axial direction using oil pressure.
DE 10 2009 051 309 A1 shows a device for the camshaft adjustment, wherein the camshaft adjuster contacts against a stop element of the camshaft with its hub and an axial tension between the camshaft adjuster and camshaft is realized by an attachment element. The attachment element is here constructed as a tensioning nut.
WO 2007/082600 shows a camshaft adjuster that is mounted by a central valve constructed as a central screw on a camshaft.
EP 1 544 419 A1 shows a camshaft adjuster that is mounted with a central screw without a valve function on a camshaft.